Letters: Browned off

Marcus L. Rowland might not be seeing Brownian motion (Forum, 13 April), but we first-year undergraduates can reproduce the experiment in minutes. Just to make sure, all three of us separately did the experiment this morning.

Paper drinking straws are obtainable, not for drinking through though. They are called art straws and they elegantly funnel the smoke into the cell. The 'special linear filament bulb' in our case is a common 12 V type used in car interior lights, hardly scarce.

We would be happy to show how it's done. Once set up properly the random dance of hundreds of glistening smoke particles is beautiful.